1. Field of Invention
The present invention relates to a backlight module and more particularly to a side-light type backlight module and its light guide plate module for being applied to local dimming technology.
2. Related Art
Local dimming is a technology for backlight source of a liquid crystal display to produce different changes of brightness on different areas of a light emitting surface. It has the advantages of enhancing the screen contrast to further improve the image quality. In general, local dimming technology is mainly applied to direct-light-type backlight module, particularly in backlight modules which employ light emitting diodes (LEDs) as the light source. Changes of brightness on specific areas are achieved by controlling the LED's brightness on different areas.
Although the combined applications of direct-light-type LED backlight module and local dimming technology can reduce power consumption and enhance screen contrast. On the contrary, the control system for LED is rather complicated, so that the costs for circuit design are increased.
Side-light type backlight modules produce planar light source via a single light guide plate, therefore it cannot control the brightness of specific areas even if local dimming technology is applied. Furthermore, it is technically difficult to manufacture single light guide plates with large area for backlight modules of large sized liquid crystal displays, the costs are therefore expensive. In addition, large sized light guide plates are easily deflected by external forces to affect the optical performance.
In order for side-light type backlight modules to be used with local dimming technology, the solution is to apply a plurality of light guide plates with independent light source control. In the R&D process, the application of a plurality of light guide plates is structurally and practically difficult to joint them flatly and evenly. Adjacent light guide plates will detach/displace and offset from each other if they are impacted by external forces or if the backlight modules are placed upside down. This will result in deformation of the backlight module sheets to affect the light emitting effects.
Therefore, it is necessary to provide a backlight module and its light guide plate module to tackle the current technical problems.